Load-carrying member



M. WATTE'R LOAD CARRYING MEMBER Aug 14, 1945.

Filed Feb. 20, 194';

a N ENTOI K Mich-gel Waiter.

. fi a i V 3 .2 1s 9 m ATTORNEY Y Aug. 14, 1945.

M. WATTER LOAD CARRYING MEMBER Filed Feb. 20, 1945 2 Sheets-Sheet 2 INVENTOR A TTORNE Y 23, Michael Watter Patented Aug. 14, 1945 LO ADCARRYING- MEMBER Michael Watten, Philadelphia, Pa., assignor to EdwardlG Budd Manufacturing Company,,, Philadelphia, Pa, a corporation ofPennsyl- Vania ApplicationlFebruaryr 20, 1943,, SeriaPNo. 476,534

5 Claims.

The invention relates to alload-carryin'gz member or girder, such as isparticularly adapted for use as the rib of an: airfoil; particularlywhere such rib is required to-carry heavy loading.

It is among the objects oi theinvention to provide sucha ribhaving ahigh strength-weight ratio; and whichcan: be readily" fabricated out oflight gauge" sheet metal, such as high-tensile stainless-steel:v

To accomplish these obj ectsthe rib structure is so designed as topermitcertain of the strength members thereof; as the chords, while conforminggenerally to the curved contour of the'ainfoil in whichtherib is to beused, to'be made oi parts of rectilinear'form, in which-form these partscan bereadily made of the desired crosssection by simple draw-rollingofa strip of the sheet metal.

It is quite diflicult to form angle or channel sections of stainlesssteel, for example; of the gauge requiredi'n such chords; was to givethe exact contour ofthe airfoil; It is desirable for maximum strengththat the chords lie as close-to the marginal contour as-possible. Ihe'difficulty is avoided and the last-mentioned desirable feature isattained by the invention by making the chords in-rectilinear'sectionsjoined atthei'r meeting ends to form the full'lengthchords.

A web plate or an extension thereof is used according to the inventionto form" the marginal cap stripcontour" forming portions of the rib.Between the chords the web plate is reinforced by a transverselycorrugated" sheet and for balance the chords are of compositeconstruction, parts located on oneside of the web and parts on theother. The chord" elements located on the side of the webplate'rei'nforced by the corrugations are further provided topreventdistortion of the ends of the corrugations under load, since these chordelements are secured to the corrugations and tothe'web plate, thus tyingthe parts strongly together. To facilitate assembling of thesechordelements and to stiffen the-chord structure still further one oftheseelements secured to the corrugations has a freely projecting portion,preferably for added stiffness, a flange portion projecting laterally ofthe web plate" and secured to the web-plate by a second element securedto the flange and the web plate andbrid'ging the ends of thecorrugations.

Other and further objects and advantages and the manner in which theyare'attained will become apparent from the following detaileddescripti'on' when read in connection with the'drawings forming aparthereof.

iii

In the drawings, Fig. l is a; chordwise sectional: view: thnoug anairfoil showing the ribs of the invention em;-

bodied therein,

Figs 2 is a similar sectional view: on; an: en;- larged scale showingthernose' end ofithe ribz.

Fig; 3' is a sectional view of the nose: portion of the rib takensubstantially-along the line.3r-3 of Fig.2;

Fig; 4 is anenlarged fragmentary-perspective view; with parts brokenaway, of? the lowenportion of the rib showing'the'joint: between; abut;-ting rectilinear chord: sections; as: seen. looking in the directionindicated by the arrowsat" the end of t'he section line-'4 -4 of?1-i'g..1; and;

Fig. dis a vertical sectional'viewthrough; the rib on substantially the.same scale as Fig. 4, taken substantially aIong'tIie Iine'E -S': of Fig:"1, part of the web-:being broken away.v

In the embodiment-oi the invention selected for illustrationtheload-carrying member on girder is shown comprising a main strength rib:of? an airfoil l0; such as=thehorizonta1 stabilizer: of an aircraft,althoughit will be understood that" the novel features thereof may beuseful in: other relations.

Referring to Fig. 1 the airfoili I0 is: shown: as having a' convexlyrcurved top and bottom and embodiesa nose portion I i an intermediatespar l2 and a rear spar l3} theseparts being strongly interconnected bya strong" rib; designated generally by Hi; and otherribs' spaced fromthe-rib l4" and from each other, but not shown herein extend chordwiseof the wing. A suitable trailing edge'portion' not shown' i's securedt'o therear spar to complete the airfoil section;

The outer marginal contour of the rib l'kl ccnforms generally to thecurvature or the airfoil.

In the nose portion, it extends outwardly 'tothe skin, and-the nose skinsheet, as l5; directly-'overlaps and is securedtothe marginal portion ofthe rib in this region. Rearwardl'y' of the nose; the marginal portionsof the rib, while conforming generally to the contour of the airfoil;are inwardly offset to receive thereinforcedskinblanket l6; l6; andtopass under the chords of the spars l2 and l-3' and besecured'theret'o: In the region between the nose and the rearspar I? theskin blanket comprises a skin sheet l 6- stifi"enedby*an innerreinforcing structure; designated-generally by I6 to which are secured aseries of c1ips; as

H" which, in turn, have their inner portionsoverlap the marginalportions of" the rib, and are secured thereto in the overlap: The-skinsheet l6 at the iront is secured by a splice'plat'e, see

nose region, see Figs. 2 and 3, Where the web.

plate extends substantially to the skin, its margin is reinforced byangles l8 and I9, the outer arms of which lie parallel to the skin sheetl and are interconnected to each other and to the skin sheet by anoverlying flat strap 20.

Rearwardly of the nose portion the margins of the web plate I! areformed by separate top and bottom cap strip extensions 2| and 22, seeFig.

5, flanged in their outer margins, as at 23 so as to give them greaterstrength and stiffness. As shown in Figs. 1 and 2, the forward ends ofthese extensions are outwardly offset to overlap both the nose web plateand the angular reinforcement, and are secured, as by spot welding, toboth. These forward offset ends, as 2| and 22, may comprise separatelyformed pieces, as shown, overlapping and secured to the forward ends ofthe cap strip extensions 2| and 22.

As shown in Fig. 5, the cap strip extensions 2| and 22 have a wideoverlap inwardly with the main body of the web plate I! and are stronglysecured thereto so as to form, in effect, an integral part of the webplate as a whole, by numerous spot welds in the overlap.

To give the web plate the characteristics of a strong load-carrying beamor girder, it is reinforced adjacent its top and bottom margins by chordmembersdesignated generally by 24 and 25. Between the chord members andto give the web plate great stiffness against buckling, it is reinforcedby a vertically corrugated sheet or sheets 26 spot welded through thecontiguous corrugations tothe web plate H. For convenience ofmanufacture, the corrugated sheet 26 may be built up in'sections withvertical overapping joints, as indicated at 21, in full lines in Fig. 4and in dotted lines in Fig. 1. In the nose portion, see Fig. 3, thecorrugated sheet extends outwardly close to the marginal angle l9 andthe chord parts 33, 34 later to be described as being located on thecorrugated side of the web, are discontinued through the .nose portion.

The chords 24 and 25 are of composite construction for convenience ofmanufacture and, to provide a substantially balanced construction onopposite sides of the plane of symmetry of the web, parts of the chordsare located on opposite sides of the web plate I1, as clearly appears inFigs. 4 and 5. The chord parts on each side of the web plate arepreferably located close to the contoured margins of the web plate butsince this would ordinarily require that they be bent to conform to thecurvature of the airfoil a special construction is provided.

Since it is desired to manufacture them of angular or channel formsections for strength and stiffness, to so bend them, particularly whenmade of high-tensile stainless steel, would require difficult bendingoperations.

Accordingly, to avoid this bending, and still attain the advantage ofhaving the chords as a whole conform nearly to the contour of themargins of the web and be located relatively close to said margins, thechords are preferably built up ,of rectilinear sections, having theirends secure- 1y joined together to form, in effect, a continuous chordmember from end to end of the rib.

As shown in Fig. 1, the chord parts overlapping the flat side of the webplate I! are each, both the top and bottom parts, built up of threerectilinear sections 28, 29 and 30. As shown, these sections consist ofshallow outwardly facing channels strongly spot welded to the doublethickness metal formed by the overlap of the body of the web plate l1and its marginal extensions or cap strips 20, 2|. The ends of thesections may abut, as shown, in the joint between sections 29, 30 shownin detail in Fig. 4, the abutting ends being overlapped by a junctionstrip 3| strongly welded to the adjacent ends of the sections, The jointmay be additionally stiffened by an angle 32 welded to the junctionstrip 3|. The junction strip, as 3|, may be extended, as shown, throughthe entire length of the intermediate section 29, and into overlappingengagement with the forward section 28, as shown, for example, at thetop of Fig. 1.

All the joints between the sections may be made in this way or, as shownat 32' in Fig. 1, the joint may. be made by cutting away the insideflange of one of the channel sections as 29, and stopping the strip 3|short of the end of channel 29 and lapping the bottom of the end of thechannel section 28 directly over the bottom of the end of the channel 29and spot welding them together in the overlap. Additional anglestiffeners, as 3|, could also be applied, if desired, to this type ofjoint. 1

Certain of the chord parts on the opposite side of the rib are similarlyconstructed in rectilinear sections joined together at their ends. Theyflank the margins of the corrugated sheet reinforcement and are securedthereto and to the web plate IT. This securing of thechord parts to themargins of the corrugations prevents the distortion of the side walls ofthe corrugations under load and adds materially to the stiffness of therib structure.

As shown in Figs. 4 and 5 the chord parts on this corrugated sheet sideof the rib are preferably fabricated, for each the-top and bottom chords24 and 25, out of two longitudinally extending channel members 33 and34. Channel member 33 is in rectilinear sections, and has one of itsside walls as 35 arranged slightly beyond the margin of the corrugatedsheet 26, and of widened construction and flanged in its margin. Thismember can readily be secured to the contiguous corrugations, after thecorrugated sheet 26 has been spotwelded to the web plate IT, byinserting. a spotwelding electrode through the ends of thecorrugations.-

'After the member 33 is so secured in place it is further stiffened andrigidly tied to the web plate extensions 2|, or 22, by the channelmember 34 which has a wide side Wall as 36, also flanged in its marginand directl welded to the adjacent plate extension and its bottom walladjacent its shallow side wall in overlapping relation with andspotwelded to the side wall 35 0f the member 33. The laterallyprojecting double thickness flange so produced adds materially to thestiffness of the chord and the entire rib structure. As indicated inFig. 4, the longitudinal sections of the member 33 may be joined by lapstrips 3| and angle reinforcements 32, in a manner similar to thejoinder of the sections 29 and 30 of the chord parts onthe opposite sideof therib. Channel member 34, because-it is more readily bent byreasonof its right angular relation, to the web plate of the rib, may bemade continuous over the various longitudinal sections of member 33..Accordingly, no lap strips are required, or shown, in connection withthis memher. It is understood, however, if difficulty in bending it atthe joints should be encountered, it may very well be constructed inlongitudinal sections and joined in the manner indicated in connectionswith the sections 28, 29, 30 and 33.

At the extreme nose portion the channel sections 28 may have theirbottom walls offset and overlapped over the marginal angle l8 andspotwelded thereto, as shown in Fig. 2. For greater strength in thisnose region the top and bottom channel section portions 28 of the chordsmay be reinforced, as shown in Figs. 2 and 3, by a flanged channelreinforcement 31 spotwelded thereto.

From the foregoing detailed description, it will be seen that a verystrong and rigid rib construlction readily fabricated from sheet metalparts and readily joined by spotwelding has been provided. However, itwill be understood that the specific construction described is merely byway of illustration and that changes and modifications would readilyoccur to those skilled in the art. Such changes and modifications areintended to fall within the scope of the appended claims.

What is claimed is:

1. An airfoil rib comprising a web plate having a marginal portionconforming to the curved contour of the airfoil, a vertically corrugatedstiffener sheet secured to said Web plate and terminating short of themarginal portion thereof, a composite chord member secured to the webplate and its corrugated reinforcement including an angular memberextending longitudinally along a margin of the corrugated sheet andsecured thereto, and having an arm projecting in a direction away fromthe web, and another longitudinally extending member secured to said armand to the web plate.

2. A load-carrying member comprising a chord and a web plate having amarginal portion extending beyond the chord, the web plate inside saidmarginal portion being reinforced by a transversely corrugated sheetsecured thereto, the chord comprising an angular member extendinglongitudinally along a margin of the corrugated sheet and securedthereto, and having a freely projecting portion beyond the margin ofsaid sheet and a second longitudinall extending mem-' berinterconnecting said freely projecting portion and the web plate.

3. A load-carrying structure having a curved outer edge, as an airfoilrib, comprising in combination, a web having marginal cap-strip portionsconforming to the curved outer edge contour, and chordal membersadjacent each edge, each chordal member including a series ofrectilinear pieces secured to the web and secured together at theirjuxtaposed ends adjacent the outer edge.

4. A load-carrying structure having a curvilinear outer edge, as anairfoil rib, comprising in combination, a plate web, a cap stripoverlapping said :plate Web interiorly and conforming to the curvilinearcontour at its outer edge, and a chordal member secured to theoverlapping portion of the web and cap strip, said chordal memberincluding a series of rectilinear elements secured together at theirjuxtaposed ends adjacent the outer edge.

5. A load-carrying structure having opposite curvilinear outer edges, asan airfoil rib, comprising in combination, a plate web, cap stripsoverlapping the plate web and secured thereto at their inner edges, thecap strips at their outer edges conforming to the required contour forcarrying the load, a segmental chord secured to each cap strip adjacentits inner edge, the chord segments being rectilinear and spliced toadjacent segments, a corrugated strut sheet secured to the plate webopposite said cap strips and chords and occupying the zone of andbetween the chords, further segmental chords secured over the outside ofthe strut sheet at the ends and opposite the first chords, and chordalstrips secured to said cap strips over the ends of said strut sheet, thechordal strips and the second said chords being secured to ether.

MICHAEL WATTER.

